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Reviewed by: HU Medical Review Board | Last reviewed: March 2023

For people who have irritable bowel syndrome with diarrhea (IBS-D), anti-diarrhea medicine for IBS is a treatment option to decrease stool frequency and improve the consistency of stool by enhancing the amount of water the gut absorbs.1,2

Antidiarrheal medicines for IBS

The most common anti-diarrhea medicine for IBS available over-the-counter is Imodium (loperamide). Another anti-diarrhea medicine for IBS is available by prescription, such as Lomotil (diphenoxylate with atropine). Another class of prescription drugs used for its antidiarrheal effects is the bile acid sequestrants, which bind to the bile acid in the intestines and reduce diarrhea caused by excessive bile acid. These drugs are not approved for IBS, as there is not a lot of evidence for use, but individual clinicians may recommend their use based on experience.3 About one-third of people with IBS-D have evidence of increased bile acid production or excretion.4

Imodium (loperamide)

Imodium (loperamide) is available without a prescription. Loperamide is a synthetic opioid that slows intestinal transit and enhances the water and ion absorption in the intestines. It has been sufficiently studied and proven effective in clinical trials for its ability to decrease stool frequency and increase stool consistency, however, it did not improve abdominal pain, another common IBS symptom.1

Lomotil (diphenoxylate with atropine)

Lomotil is a prescription drug for diarrhea. However, Lomotil has not been studied in people with IBS.1 The active ingredient in Lomotil, diphenoxylate, acts on the smooth muscle of the intestinal tract, inhibiting excessive movement and slowing intestinal transit. Lomotil is potentially addictive, and atropine is added to the compound to discourage deliberate overdose.2,5

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When taking Lomotil, symptoms are generally improved within 48 hours. If there is no improvement, it is unlikely the drug will be effective. Side effects may include blurred vision, sedation, nausea, vomiting, abdominal discomfort and dryness of skin or mouth.5

Lomotil comes in an oral solution or capsule (2.5 mg). Patients are generally prescribed 5 mg every 6 hours, not to exceed 20 mg daily.5 Overdose is possible and can lead to serious symptoms, including a blockage in the bowel, coma, hallucinations, slow breathing or breathing that has stopped. If an overdose occurs, call for emergency medical help immediately.6

Prevalite (cholestyramine)

Prevalite is a prescription drug that binds to the excess bile acid in the intestines so it can pass out of the body.7 Prevalite may be considered for the treatment of diarrhea with IBS after people have tried Imodium (loperamide).8 It comes in a powder that must be mixed with fluids or food and can be taken before or with meals.

Side effects may include burping, constipation, diarrhea, gas, gallstones, heartburn, nausea, vomiting, pancreatitis, rectal pain or irritation, and malabsorption of fat-soluble vitamins (vitamins A, D, E, and K). People who are allergic to bile-sequestering drugs or who have blockages in their bile duct should not use Prevalite.7

Cholestyramine interacts with many medicines, so check with your pharmacist about taking it apart from your other daily medicines.

Colestid (colestipol)

Colestid is a prescription drug that is approved to lower high cholesterol by binding to the excess bile in the intestines. After a drug is approved for use, experience may show that it is also useful for other conditions. Doctors may prescribe Colestid to treat diarrhea caused by excess bile acids.9

Colestid may cause constipation, burping, nausea, vomiting, gas, diarrhea, anxiety, or fatigue. Rarely, people taking Colestid experienced gastrointestinal bleeding, gallstones, stomach ulcers and malabsorption of fat-soluble vitamins. Colestid should not be used by people who are allergic to colestipol or who have a bowel obstruction.10

Welchol (colesevelam)

Welchol is a prescription drug that binds to excess bile acid in the intestines and reduces cholesterol. It has also been studied for its effects on reducing diarrhea in people with IBS-D.4,11 In clinical trials, Welchol was associated with a significant reduction in both bile acid excretion and significantly more solid stool consistency. In addition, people experienced fewer bowel movements after using Welchol for several days.

Welchol is a tablet taken by mouth with meals. Side effects may include gas, constipation, nausea, diarrhea, abdominal pain, weakness or muscle pain. If a person experiences severe abdominal pain with or without nausea and vomiting, they should contact their doctor immediately.11

Other treatment options for IBS

Most people with IBS find a combination of treatment approaches work best to manage their symptoms. Other treatment options to consider include

  1. Adding fiber or probiotics
  2. Making dietary changes
  3. reducing stress
  4. Adding exercise
  5. Using complementary or alternative treatments

These are not all the possible side effects of antidiarrheal medicines. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with antidiarrheal medicines.

Before beginning treatment for IBS, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.